1. Field of the Invention
The present invention relates to flooring systems, and in particular relates to suspended concrete flooring systems for use in residential and commercial construction projects.
2. Description of the Related Art
Suspended flooring systems are gaining popularity for both residential and commercial construction projects. This is increasingly true for projects on sloped construction sites. Traditionally, a sloped site must be leveled by cutting away a suitable area for a foundation, and then erecting substantial retaining shoring to uphold the surrounding terrain. This is often costly, and thus, suspended flooring systems offer an attractive alternative because the land does not have to be substantially altered before construction can begin.
Additionally, consumers have expressed a preference for concrete floors over wooden floors because of its smooth, flat surface that does not bow or warp, it is silent and does not squeak, it is fire resistant, and it is resistant to termite and water damage. Although consumers have expressed a preference for concrete flooring, many consumers are forced to settle on suspended floors constructed of wood because of its cost advantage over concrete suspended flooring. Generally, suspended concrete floors are both material and labor-intensive and are thus often cost prohibitive regardless of the construction technique.
There are currently a variety of construction techniques for producing suspended concrete floors for single and multi-story buildings. One such method of forming a floor in situ involves pouring concrete into an arranged formwork. In order for this type of floor to perform structurally, the concrete must be quite thick. This results in a floor that is very heavy and therefore requires a significant amount of formwork to hold the floor in place. Furthermore, the substantial amount of concrete results in a floor that is very expensive to install. One way of reducing the cost and weight considerations involves incorporating steel reinforcement into the floor to provide increased tensile strength which allows a thinner concrete slab. However, the substantial formwork necessary is labor intensive and usually makes this option cost prohibitive, especially for residential construction projects.
Another construction technique involves positioning pre-cast slabs or beams into an arranged framework. This method involves less supportwork than traditional poured floors; however, pre-cast slabs or beams are generally too heavy for manual installation and this technique often requires the use of heavy machinery, such as cranes, to position the heavy slabs into the framework, which makes construction projects on sloped construction sites problematic. Additionally, the slabs or beams must be poured and cured off-site and then hauled to the construction site. Not only are there additional costs associated with delivery of the slabs, but the additional handling of the cured slabs, (e.g. truck loading and unloading, lifting the slabs with a crane, positioning the slabs into the framework) presents opportunity for the slabs to become damaged.
Regardless of the construction technique used, an important consideration is the system used to support the concrete floor during construction. Generally, a concrete floor cannot go unsupported over a large span during construction because of its inherent relatively weak tensile strength. Therefore, a significant amount of underlying supportwork is often required to provide adequate structural support for the floor during construction. The installation of the supportwork, usually in the form of framework or formwork, in preparation for such a floor is a predominant component of the labor cost, and often makes large floors economically infeasible.
Accordingly, the ability to span a large area of floor with a minimum of supports during construction is a significant challenge in construction, and is a constant goal of suspended concrete flooring system design.
One approach to strengthening the cement, thus allowing it to span larger unsupported distances, is to incorporate fibers such as steel, asbestos, glass, or synthetics into the cement composite. Two commercially available reinforcing agents are asbestos and glass fibers. Asbestos is an important cement reinforcing material because of its chemical and thermal inertness, fibrous structure and high modulus of elasticity. However, health risks associated with the manufacture of asbestos-cement based materials have restricted their use in recent years. Asbestos-based cement composites also often exhibit brittle failure, while glass fiber reinforced cements are sensitive to age and curing, reducing the efficiency and desirability of these reinforcing agents.
Synthetic fibers are excellent alternatives to supplement or replace glass and asbestos fiber reinforcing agents. Acrylic fibers are one of the most important types of fibers as reinforcing agents for ambient-cured cement composites. These materials offer a high modulus of elasticity, good alkali resistance and good adhesion when properly oriented in a cement mix. Wet stretch, plastic stretch or heat-transfer fluid mediated stretching techniques assure fiber orientation in the composites, which is required for high modulus characteristics.
Fiber reinforcing a cement composite gives it the advantageous characteristics of higher tensile strength and a higher modulus of elasticity. These improved characteristics allow the cement to maintain its structural integrity over greater unsupported spans, achieve sufficient structural strength with less material, and offer a reduced cost option because less material is required. Accordingly, it would be advantageous to have a suspended concrete flooring system that takes advantage of the properties of fiber cement products to make such flooring systems more applicable to residential use. It would be a further advantage for a flooring system to combine the benefits of the above-mentioned flooring systems while eliminating the drawbacks of each.
The preferred embodiments disclosed herein solve the above-described problems by combining, among other things, the prior art methods of positioning pre-cast concrete slabs or beams and pouring a floor in situ. Specifically, a pre-cast floor has the benefit of requiring a minimal amount of supportwork, while the poured floor offers the benefits of creating a monolithic floor without the need for slab transportation and heavy machinery installation. This is accomplished by making use of a rigid framework supporting corrugated fiber cement sheets to provide an underlying support layer for a poured in situ concrete floor. The framework includes strong, lightweight load-bearing members or supporting walls and joists arranged so as to allow for a large floor span between supports.
The result is a monolithic concrete floor that is easily constructed, can be installed manually without the need for large machinery, and can span larger unsupported distances thus reducing the necessary framework, installation time, and labor cost.
A first aspect is a cement flooring system suspended above the ground either by a plurality of spaced-apart load-bearing members or supporting walls arranged substantially parallel to one another supported by traditional footings. The system further includes a plurality of spaced-apart joists having opposing sides and arranged at substantially right-angles to the load-bearing members or supporting walls and are supported thereby. Each joist, except perhaps for the outer joists, has a support shelf formed along the length of each opposing side. The system also includes a plurality of deck sheets supported between the joists by the support shelves so as to span the space between the joists in the horizontal plane defined by the support shelves and provide a substructure to receive the poured concrete. In one embodiment, the deck sheets are corrugated fiber cement sheets. A shrinkage control mesh is arranged atop the joists and is oriented in the directions of the load-bearing members and the joists. A concrete topping layer is poured atop the corrugated fiber cement sheets and encompasses the shrinkage control mesh. The concrete topping layer is formed to have a flat, horizontal upper surface that serves as a floor.
A second aspect is a method of installing a concrete flooring system suspended above the ground in which a plurality of footings have been previously installed. The method includes the step of first arranging a corresponding pier on each of the footings. The second step involves positioning and securing a plurality of load-bearing members atop the piers. Alternatively to piers and load bearing members, support for the joists can be in the form of supporting walls, such as masonry walls. The third step comprises positioning and securing a plurality of spaced apart joists to the plurality of load-bearing members or supporting walls at substantially right angles so that the joists are supported by the load-bearing members or supporting walls and define a space for receiving the fiber cement corrugated sheets. The fourth step includes placing a plurality of fiber cement corrugated sheets in the space between the joists so as to be supported in a horizontal plane by the joists and to span the space between the joists. The fifth step involves arranging a shrinkage control mesh atop the joists in orientation with the load-bearing members and the joists. The final step includes pouring concrete over the corrugated sheets so as to encompass the shrinkage control mesh and to form a flat horizontal floor surface.